Process and apparatus for the production of coke



O 1962 H. HOFFMANN ETAL PROCESS AND APPARATUS FOR THE PRODUCTION OF COKE Filed Nov. 6. 1957 DENSITY IN TESTS 1'19 CHARGE 4 Sheets-Sheet 1 42:0 42, 41,0 .321 39,0 as 32/ 410 42a .qa go 9,0 0;! a!

//V VENTORS Heinrich HOFFMANN 1952 H. HOFFMANN ETAL 3,058,891

PROCESS AND APPARATUS FOR THE PRODUCTION OF COKE 4 Sheets-Sheet 2 Filed NOV. 6. 1957 IN VE N 7" 0R8 Heinrich HOFFMANN Josef SCHMIDT FP/fPI/C/I fly- 760f Oct. 16, 1962 H. HOFFMANN ETAL 3,

PROCESS AND APPARATUS FOR THE PRODUCTION OF COKE Filed NOV. 6, 1957 4 Sheets-Sheet 3 Oct. 1962 H. HOFFMANN ETAL 3,058,391

PROCESS AND APPARATUS FOR THE PRODUCTION OF COKE Filed NOV. 6. 1957 4 Sheets-Sheet 4 Hem/'12: HOFFMAN/V Josef SCH/VIN nite tats atent iifice Efifihfil Patented Oct. 16, 1962 3,058,391 PROCESS AND APPARATU FQR THE PRODUC- TI'SN F COKE Heinrich Hofi'mann, Volidingen (Saar), and Josef Schmidt and Friedrich Thiersch, Reckiinghausen, Germany, assignors to Riichiingsche Eisenand Stahlwerire G.m.b.H., Volkiingen (Saar Germany, and Firma Carl Still, Recklinghausen, Germany Filed Nov. 6, 1957, Ser. No. 694,804 Claims. (Cl. 20226) The present invention relates, in general, to a process and apparatus for production of coke in batteries of selffeeding coke ovens, and more particularly to the production of coke for use in a blast furnace, wherein said coke is made from moist, finely ground coal mixtures which are not suitable for normal self-feeding, and especially mixtures which are rich in gas.

It is to be remembered that when using moist coals which are inapt for normal self-feeding, particularly coals which are rich in gas for the production of blast-furnace coke, the density of the oven charge is an important factor. The bulk density of these coals, which is obtained in the usual self-feeding of good coking coal, is not sufficient to ensure an adequate plastic bonding of the coal granules to form compact and firm coke in suitable large pieces, such as is required for metallurgical purposes. Therefore, various attempts have been made in order to obtain a higher bulk density.

One attempted solution of this problem, for example, was achieved by stamping the coal and using the thus obtained compressed coal cakes in the oven. Nevertheless, this stamping operation involved considerable expenditures, and moreover, certain attendant disadvantages ensued during the aforementioned stamping operation.

One serious disadvantage was that a considerable limitation was imposed on the selection of the height of the oven, as a result of which the efiiciency of the oven operation suffered greatly. A further disadvantage was due to the fact that the compressed coal cake was stable, and hence, the degree of compression of said coal had to be carried to excessive lengths with the result that the formation of cracks in the coke was incurred.

Consequently, a compressed coal coke which is broken as the chamber is charged results in a considerable drop in the efliciency of the oven, together with extreme difficulty in emptying said ovens. Thus, while the density of the oven charge is too low in normal self-feeding, with stamping the density is too high.

The most favorable density of the oven charge for the processing of moist, finely ground coal mixtures which are inapt or ill-suited for normal self-feeding, particularly mixtures which are rich in gas, should lie somewhere between these two values.

It is already known to coke coal mixtures in which coarse granules are present in larger proportions than fine granules. In the aforementioned process it was proposed that briquettes of substantially the same or not very different sizes should be used as coarse granules, the fine granules having a proportionate size of at least 1:5 or more in relation to the smallest size of briquette. The sizes of said briquettes were preferably 50 to 80 rmn. and the size of the granules of the fine coal from O to mm., the largest granule size preferably being 2 mm. The fine granular components having granular sizes below 0.5 mm. may, if necessary, be subjected to br-i quetting. The amount of briquettes should be about twothirds by weight of the coal used so that only about onethird of the coal used consists of fine granules.

As is readily evident from the above description, the aforementioned process required extensive preparation and sorting of the coal before it could be used in the blast furnace, and the obtaining and maintaining of a uniform mixture of briquettes and fine coal is relatively complicated and extremely costly.

It is therefore a primary object of the present invention to provide means facilitating manufacture of a greatly improved coke for use in a blast-furnace which permits operation of said blast furnace with increased efliciency.

Another important object of the present invention is the provision of means contributing to relatively inexpensive and economically profitable production of a greatly improved coke for use in a blast furnace and like combustion chamber.

A further object of the invention is to provide means conducive to a formation of substantially uniform briquettes having practically the same strength in order to obviate any sorting operation which was heretofore required.

Still a further object of the invention is the provision of means contributing to the production of blast-furnace coke of the aforesaid type having a bulk density which affords highly efiicacious operation of said blast furnace.

An ancillary object of the invention is the provision of means redounding to a simplified, yet highly eflicient metallurgical coke which does not necessitate extensive preparation and sorting mechanisms as was heretofore required.

Yet another object of the invention is the provision of means leading to the production of coke from coal mixtures which were formerly inapt for use in a blast furnace.

In the course of detailed experimentation, it has been found that in practical operation great difficulties arise in attempting to achieve a uniformly distributed mixture of briquettes and fine granules in the coking chamber, or in obtaining sufficient briquettes in unbroken form in the coking chamber, such as is necessary for the de-' sired high bulk density.

All these difiiculties are now overcome in a simple and surprising manner by the method and device according to the present invention.

A characteristic feature of the method of the present invention consists in forming briquettes from fine coal having a predetermined granular size and a predetermined moisture content, said formed briquettes having a predetermined minimum weight. Thereafter care is taken to ensure that the briquettes, together with part of their seam, remain largely unbroken until they enter a coking oven chamber. Under certain conditions it has proved desirable to add a certain percentage of coke dust or low-temperature coke to the charging coal.

Furthermore, a suitable binding agent may be employed in order to aid in obtaining the desired strength of the briquettes thus formed.

The apparatus enabling the aforementioned objects to be achieved constitutes a fine-coal feed device, which is adapted for measuring a quantity or dosage of fine coal, so that the latter has adequate strength for a pressure loading of a predetermined value. The thus measured coal is then fed into a briquetting press comprising two counter-rotating rollers, which forms briquettes having the properties detailed previously. The briquettes are thereafter introduced into a charging car bunker, preferably with the aid of a suitable conveyor, which is constructed and arranged so that the path of fall of the briquettes through filler holes into the coking chamber is kept at a minimum. Therefore it is ensured that said briquettes remain largely unbroken upon entering said coking oven so that several briquettes decompose into fine-grain material, and form a bed for subsequently fed unbroken briquettes which are also received in said coking oven chamber.

The above and other objects of the invention will become further apparent from the following detailed description, reference being made to the accompanying drawings showing preferred embodiments of the invention.

FIG. 1 shows graphically the results of a series of tests performed on the coke produced in accordance with the present invention; a

FIG. 2 is a longitudinal, elevational sectional view of the apparatus pursuant to the present invention; FIG.- 3 shows the arrangement of the charging car disposed over'the top of the coking oven;

FIG. 4 shows a section through the briquetting roller press taken along line IV-IV of- FIG. 5; V

FIG. 5 shows another section taken along line V-V of FIG. 4; and c 7 FIG. 6 shows schematically, in an enlarged scale, the pressed string of coal, disclosing the manner in which the string breaks upinto individual, double, or even triple briquettes at first, after emerging from the briquetting press.

Referring now to the drawings, a -,device for carrying out the method will now be described by way of example, with particular reference to FIGS. 2 to 6.

The arrangement of the apparatus seen in FIG. 2 discloses a substantially frusto-conical shaped coal bunker 1 which is adapted to hold'fine coal, said bunker being provided with a discharge opening in. A chain conveyor 2 is arranged below the discharge opening of said coal bunker which contains fine coal of predetermined size.

A discharge conduit or pipe 3 which eads from the chain 7 conveyor 2 to a feed hopper 4 is disposed above a double roller briquetting press 5. The feed hopper 4 is provided with a vibration device 6 which serves to measure out a predetermined quantity or dosage of said fine coal received from the coal bunker 1 before the same enters the press 5. This vibration device 6 may, to advantage, be adjustable in order to control the movements of the hopper 4, so that the amplitude and/or frequency and/or direction of the vibratory movements in one ormore dimensions of said feed hopper may be controlled. The

string of coal coming from the roller briquetting press 5 breaks up irregularly as it reaches a shaking conveyor trough 7, or any other suitable conveyor means which may be placed beneath said roller press, as for example, a chute. The shaking conveyor trough 7 delivers the briquettes in a gentle and careful manner to the buckets 8 of the rotating bucket conveyor 9 which is located adjacent one end of said trough, said bucket conveyor being further adapted to be raised or lowered, and is supported, for example, by means of a hook located on a pulley 31. Said bucket conveyor may also be replaced by a vibrating spiral conveyor which can also be raised or lowered, many other suitable conveyor means. The distance between the shaking conveyor and the bucket conveyor is so controlled that the height or path of fall of the briquettes is kept at a desired minimum. The bucket con-' veyor 9 extends towards a charging car bunker 10, so that the briquettes carried by the buckets 8 reach said bunker likewise with the minimum possible height or path of fall. The arrangement may conveniently be such that one briquetting press supplies two or more substantially frusto-conical shaped charging car bunkers through the intermediary of a plurality of suitable conveyor means.

During the course of filling the car bunker 10 the bucket conveyors 9 are rotating and hence'are raised. Mounted below the narrowest or smallest cross-sectional opening 11 of the charging car bunker is a cover or closing member 12, said closing member being further disposed above an annular chamber or jacket 13. Said jacket is situated adjacent to and in alignment with said narrow opening through which the compressed coal drops freely by gravity towards a plurality of filler holes or openings 14 located in the coke oven, and thence finally into the oven chamber 15, as can best be seen in FIG. 3.

press breaks up in the form of separate It is important to make the respective lower openings in the annular jackets 13 surrounding the charging car bunker closures 12 and the filler openings or holes 14 in the coke oven substantially the same size as, or slightly smaller than, said narrowest cross-sectional opening 11 which is located above the charging car bunker closures 12; the geometrical shape of the narrowest crosssections 11 corresponds preferably to that of the jacket openings or apertures and the filler holes. In other words, said openings may be rectangular or circular, as desired. Rectangular filler holes should then preferably be provided with round covers, which may be doublelayered.

In order to facilitate the emptying of the chargmg car bunkers, and hence, to shorten the chamber charging time, which is known to have a favorable effect on the bulk density, suitable vibration devices with adjustable amplitude and/or adjustable frequency and/or direction of vibratory movement in one or more dimensions may be mounted on the charging car bunkers.

A charging jet or guide funnel 16 may be advantageously provided inside of the annular chamber or jacket 13, in which case the current of air produced by the charging jet may pass out of the annular chamber 13 between the funnel 16 and said chamber through a chimney-like extraction pipe 17 into the atmosphere.

In FIG. 4 there are shown the counter-rotating rollers 20 ofthe briquetting press 5, said rollers being provided with substantially arcuate, semi-circular recesses or cavities 21 predeterniinently spaced along the periphery of said. rollers, preferably at a distance of 10 to 15 mm. The string of coal 22 emerging from the briquetting broken pieces and slides down onto the shaking conveyor trough 7,

v Thereafter,

and thence to the buckets to be subsequently carried to the coking furnace.

In FIG. 6 there is shown the irregular breaking up of the string of coal 22 into individual pieces 24, pieces 25 including two briquettes, whereas pieces 26 include three briquettes together with an intervening area 27. The briquettes thus formed may be egg-shaped, drop or finger-shaped.

The characteristic features of the method according to the present invention, which is performed by means of the heretofore described apparatus, consist in that the fine coal having a maximum granule size of 1 to 3 mm., preferably 2 mm. and having a moisture content of less than 11%, preferably 6 to 8%, before being introduced into the charging cars, is formed in a suitably equipped and adapted briquetting means, such as -a press, into briquettes having a weight of more than 35 g., prefer ably 50 to 100 g. and having a seam of more than 2 mm., preferably about 10 to 15 mm. thickness, which, after the briquettes have left the press, breaks off irregularly forming compressed areas of various sizes.

care is taken to ensure that the briquettes, together with part of the flange-shaped seam or web, remain largely unbroken until theydrop into the coking oven chamber.

A further feature of the invention may be seen in the fact that briquettes having a width or length of 40 to mm. are produced by means of a predetermined fine-coal feed device which is adapted for meas uring a dosage of said coal in such a manner that the volumetric weight (specific gravity) of said briquettes is at least 1.05, preferably 1.14 to 1.18, thereby ensuring that their strength is adequate so that they will not break in the charging cars.

It has further been found to be advantageous to produce the briquettes by means of two counter-rotating rollers with symmetrical or matching mold cavities having a width or length between 40 to 80 mm., the distance from their edges or borders being at least 4 mm., preferably 5 to 10 mm. The distance between the peripheries of the rollers is more than 2 mm. and preferably to mm. As a result of the aforementioned construction of the press, one of the advantages which ensues is that the frequently encountered tailing apart or severance of the briquettes into two parts is prevented.

In order to prevent, as far as possible, breaking of the briquettes before dropping into the coking chamber, it is advisable to introduce the briquettes from the press into the charging cars, if necessary with the interposition of intermediate conveyor means, by means of a bucket conveyor or vibratory spiral conveyor, which can be raised and lowered, to provide a small path or height of fall of the briquettes so that they remain largely unbroken.

In order to obtain a satisfactory bulk density, it has further proved particularly important and advantageous that the compressed charging coal should drop freely through the tiller holes into the coking chamber from the narrowest cross-section at the bottom of the individual charging car bunkers, after the closure member provided underneath them is opened. With this mode of operation, for example, with ovens 6 m. high, there has been a shortening of the charging time to less than 15 seconds, which has had a considerable eifect on increasing the bulk density. It is also an advantage to draw off into the atmosphere the current of air produced by the charging jet which is located in the annular chamber, as by means of the previously described chimney.

-Now in order to be able to produce a useful blastfurnace coke from extremely unsuitable charging coal, as for example, coal rich in gas or a highly volatile charging coal, by the method according to the invention, it is advisable, in certain circumstances, to add a certain percentage of coke dust to the charging coal in order to slow down the reaction of said highly volatile coal. Instead of coke dust, low-temperature coke may also be used, in which case the low-temperature coke may be produced either by the flowing dust process or in the form of solid pieces. In the latter case, the low-temperature coke must be suitably finely ground before being added to the charging coal. Of course, depending on local conditions and the properties of the coal as it is found in its natural environment, the coke dust as well as the low-temperature coke can be added in predetermined quantities.

Provided the natural coal permits, it is also an advantage to include flaming coal in the process, which also may be added to the charging coal in predetermined quantities.

If the desired strength of the briquettes cannot be obtained without the admixture of a separate binding agent, a suitable binding agent, uniformly distributed, may be added to the charging coal before the latter enters the briquetting press. Examples of suitable binding agents are sulphite waste liquor or a residual oil or flotation concentrate, which is obtained during the preparation of the coal. The nature and amount of the additives are determined by the fact that, from the particular charging coal to be processed, briquettes have to be produced of such a strength that, on the one hand, they remain largely unbroken until they fall into the coking chamber and, on the other hand, bed down in the coking chamber to form a uniformly distributed mixture of briquettes and fine coal.

In FIG. 1 there is shown a graphic illustration of a series of tests 1 to 19, where the abscissa denotes, respectively, the influence of the briquett'e sizes (measured in grams), the water content (measured in percentages), and the charging time (measured in seconds) on the bulk density in a 6 m. high oven. The ordinate of the graph denotes the average bulk density, measured in kg./m. (dry), of the oven charge.

The shortening of the charging time, starting with test 12, in comparison with the preceding tests, is attributed to the fact that from this point on care was taken to ensure that the compressed charging coal received from the lowermost, narrowest cross-section 11 of the charging car bunker fell freely through the filler holes 14 into the coking chamber 15, after having rapidly opened the underneath arranged cover or closure member 12. It is further to be noted that the air and gas stream created by the charging jet was drawn into the atmosphere by means of a chimney 17 secured to the annular chamber 13, which chamber surrounds the charging jet. As a result, it can be readily observed that the charging time was considerably shortened, as seen from the graph and those tests where the bulk density is in a range between 781 to 796 kg./m. (dry).

The dashed or broken line A appearing on this graph represents the bulk density of an unbriquetted charge, whereas the full line curve B represents the bulk density of the charge which was obtained after performing the aforementioned individual tests.

The general upward tendency or increase in the value of the bulk density obviously results from the increase in the weight of the briquettes, which increase was obtained partly by enlarging the mold cavities in the press and partly by increasing the string of coal.

The drop in value in tests 6 and 7 resulted from excessive compression or pressing of the briquettes, while the drop in test 16 is attributable to a comparatively high water content in the charging coal.

This highest value of 805 kg./m. was finally obtained with charging times of about 14 seconds, a water content in the charging coal of about 6.8% and with the maximum weight of the briquettes which can be obtained at present with the existing devices, of about 47 to 48 g. A further improvement in the results of the bulk density is obtained with an additional increase in the size of the briquettes.

By the method and device according to the present invention, however, a whole series .of important advantages ensue which are simultaneously combined to provide a suprising general technical advancement in the art. The process, according to the invention, of producing coke for use in a blast furnace from inapt or nonsuitable, moist, finely ground coal mixtures obviates the aforesaid often encountered disadvantages and presents the following important advantages:

(a) The whole of the finely ground charging coal is processed to form briquettes of practically the same strength with a considerably increased press output in comparison with the usual briquetting, so that special sorting is eliminated.

(b) The regulating of the strength of the briquettes is considerably easier as a result of conveying a coherent string of coal through a roller press than when individual briquettes had to be formed.

(c) The string which breaks off irregularly after emerging from the roller press leaves behind and around each briquette a corresponding irregular flange-shaped seam which is pressed particularly hard, and the material breaking off in between in the form of areas of various sizes likewise remains compressed and contributes to the increase in the bulk density. As a result of their odd seams, the briquettes do not have an undesirable tendency to roll, and the seam further prevents splitting of the briquettes into halves at their edge.

(d) The adjusting of the water content in the charging coal to the optimum range considerably increases the bulk density of the charging coal.

(e) The risk of separation is avoided as a result of the fact that, because of particularly careful conveying, it is mainly briquettes which fall into the oven chamber.

Each bn'quette which decomposes into fine-grain material forms a bed for the next unbroken one, adapting itself to the others shape in such a manner that the largely uniformly distributed mixture of briquettes and fine-grain material, which has already been recognized as the optimum, is surprisingly formed in the coking chamher, and leads to a blast-furnace coke of the best quality during its coking.

It will therefore be apparent that the process and apparatus described herein is well adapted for achieving the heretofore mentioned objects.

Various changes and modifications may be made without departing from the spirit and scope of the present invention and itis intended that such obvious changes and modifications be embraced by the annexed claims.

Having thus described the invention, What is claimed as new and desired to he secured by Letters Patent is:

1. A method for the pretreatment of finely ground coal mixtures especially those rich-in gas and unsuitable for normal bunk handling and their introduction into a coke oven battery for the production of blast-furnace coke; comprising the steps of forming from said coal mixtures charging coal having a maximum granule size from 1 to 3 mm. and a moisture content from about 6 to 11%, compressing said 'cha rging coal into briquettes having a weight of more than 35 grams to about 100 grams and united by Web means therebetween having a thickness of more than 2 mm. to about 15 mm. thereby to obtain a row of briquettes which breaks up irregularly and presenting compressed briquette areas of various sizes, and feeding the briquettes together with at least part of their web means largely unbroken into the coke oven.

2. A method according to claim 1, said maximum granule size being about 2 mm., said moisture content ranging from 6 to 8%, said briquette weight amounting from 50 to 100 grams, and the thickness of said web means being about 10 to 15 mm.

3. A method according to claim 1, wherein said biriquettes have a volumertic weight of more than 1.05, rang ing between 1.14 to 1.18 g./cm.

4. A process for increasing the bulk weight of coke oven feeding material comprising direct-ing fine coal be tween cooperating pressure roller means to form compressed blanks including relatively lightly compressed brick portions and tightly packed web portions connecting said brick portions, and conveying the pressed blanks t0 the coke oven in a manner to insure that'the Web portions do not break away completely from each bn'ck portion and that several connected blanks with irregularly broken webs fall into the coke oven with those portions of the blank which fall apart into finely divided ma terial so that the finely divided material envelops the integral brick and connected web portions.

5. A process according to claim 4, including adding a binder such as sulphite Waste liquor to the finely divided coal as it is formed into blanks.

References Cited in the file of this patent UNITED STATES PATENTS 1,415,202 Smith May 9, 1922 1,549,141 McGregor Aug. 11, 1925 1,593,697 Illingworth et al July 27, 1926 1,610,295 Latham Dec. 14, 1926 1,893,417 Komarek Jan. 3, 1933 1,912,002 Loebell May 30, 1933v 2,075,931 Eades Apr. 6, 1937 2,204,019 Koppers June 11, 1940 2,310,748 Pearson Feb. 9, 1943 2,353,753 Otto July 18, 1944 2,556,154 Kern June 5, 1951 2,675,304 Komarek Apr. 13, 1954 FOREIGN PATENTS 5,018 Great Britain AD. 1915 356,236 Great Britain Sept. 7, 1931 533,737 Germany Sept. 18, 1931 155,372 Australia Feb. 23, 1954 735,026 Great Britain Aug. 10, 1955 1,107,922 France Jan. 6, 1956 744,432 Great Britain Feb. 8, 1956 787,195 Great Britain Dec. 4, 1957 OTHER REFERENCES Application of Low Temperature Carbonization, Chemical Engineering Progress, January 1954, vol. 50, No. 1, pp. 3-7. 

1. A METHOD FOR THE PRETREATMENT OFINELY GROUND COAL MIXTURES ESPECIALLY THOSE RICH IN GAS AND UNSUITABLE FOR NORMAL BUNK HANDLING AND THEIR INTRODUCTION INTO A COKE OVEN BATTERY FOR THE PRODUCTION OF BLAST-FURNACE COKE; COMPRISISNG THE STEPS FO FORMING FROM SAID COAL MIXTURES CHARGING COAL HAVING A MAXIUM GRNAULE SIZE FROM 1 TO 3 MM. AND A MOISTURE CONTENT FROM ABOUT 6 TO 11%, COMPRESSING SAID CHARGING COAL INTO BRIQUETTES HAVING A WEIGHT OF MORE THAN 35 GRAMS TO ABOUT 100 GRAMS AND UNITED BY WEB MEANS THEREBETWEEN HAVING A THICKNESS OF MORE THAN 2 MM. TO ABOUT 15 MM. THEREBY TO OBTAIN A ROW OF BRIQUETTES WHICH BREAKS UP IRREGULARLY AND PRESENTING COMPRESSED BRIQUETTE AREAS OF VARIOUS SIZES, AND FEEDING THE BRIQUETTES TOGETHER WITH AT LEAST PART OF THEIR WEB MEANS LARGELY UNBROKEN INTO THE COKE OVEN. 